In a small bowl, combine gochujang, gochugaru, sugar, grated garlic, apple, soy sauce, sesame oil, kimchi juice, and 1 tbsp sesame seeds. Mix until well combined then set aside.
Cook the somyeon noodles according to the package instructions, about 3 minutes. Strain then thoroughly rinse under cold water.
Transfer the rinsed somyeon noodles into a mixing bowl. Pour the sauce on top then mix until the noodles are well coated.
To serve, transfer the noodles into a bowl. Garnish with kimchi, cucumbers, a hard-boiled egg, and sesame seeds.